The present invention relates to a vibration damper for use in a disk brake to prevent the disk brake from squeaking by damping its vibration, a leading cause of squeaking, in a positive manner.
Unexamined Japanese Patent Publications 4-54324 and 4-54325 disclose such vibration dampers for positively preventing squealing of the disk brake in a positive manner. Either of these vibration dampers has a piezoelectric element for detecting the vibration of the pads and vibrating the pads in such a direction as to cancel out their vibration based on the detection signals, thereby damping the vibration of the brake.
If in such a prior art device a piezoelectric element is used to directly detect the vibration of the pads and directly vibrate the pads, the piezoelectric element 1 is buried in a caliper 2 as shown in FIG. 1A so as to press one of the pads 3.
In this arrangement, the force with which the piezoelectric element 1 presses the pad 3 depends upon the length A of the portion of the piezoelectric element buried in the caliper. If the length A is too long compared to the thickness of the piezoelectric element, it is impossible to press the pad 3 with the piezoelectric element 1 and thus detect the vibration and impart vibration to the pads. If too short, the pad 3 is pressed solely by the piezoelectric element, causing stress concentration in the piezoelectric element 1. Such stress concentration may lead to the destruction of the piezoelectric element 1. As described above, in the conventional arrangement, the length of the portion of the piezoelectric element 1 buried in the caliper largely influences the vibration detecting and imparting function of the vibration damper as well as its reliability. Thus, it is necessary to machine this portion with an accurate length.
Also, as shown in FIG. 1B, in the prior art arrangement, the piezoelectric element 1 buried in the caliper protrudes from the pad pressing surface of the caliper when the pads are removed. Thus, it tends to be caught by a pad and broken when replacing the pad.
An object of the present invention is to solve these problems.